Composition for coating and coating film obtained therefrom

ABSTRACT

Provided is a composition for coating that can form a waterproof siliceous coating film. To impart water resistance to a film formed by binder of alkali silicate, radioactive material. is used in combination with the binder. Additionally, inorganic filler, inorganic body pigment, inorganic color pigment, additive, and water are used in combination, thereby attaining a coating film that combines water resistance, acid resistance, and non-flammability.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a composition for coating and, moreparticularly, to a composition that can form a coating film having waterresistance, acid resistance and non-flammability merely by applying itto the surface of metal such as aluminum, stainless steel and iron, orthe surface of a base material such as concrete, ceramic, stone, cementmanufacture, wood, paper, and fabric, or the surface of an inorganiccoating film, and then performing air-drying or heating at lowtemperatures for a short period of time. This coating film can thereforecontribute to the corrosion prevention of concrete buildings, thecorrosion prevention of metals, and the prevention of spreading fire andsmoke pollution during a fire.

2. Description of the Background Art

A variety of compositions for coating (hereinafter referred to simply asa “composition”), which are used for forming a coating film thatcombines water resistance, acid resistance and non-flammability on thesurface of a base material, have traditionally been proposed, andvarious compositions using binder of alkali silicate are disclosed.

Specifically, it is known that alkali silicate such as sodium silicate,potassium silicate and lithium silicate can form a dry film or curedfilm by air-drying or heating at temperatures of 500 to 800° C. Althoughthese are used as binder for forming a coating film having acidresistance and non-flammability, there is a problem that a film formedby drying alkali silicate at ordinary temperatures has poor waterresistance. Therefore, in order to impart water resistance to a filmformed by a composition using alkali silicate as binder, there has beenproposed a method of using a composition in combination with acid orbasic material as curing agent. In other words, alkali silicate exhibitsalkality in strong acid solution, and hydrate of silicate in pure wateracts as acid (see page 60, “Water Glass” written by Meyer. H.,translated by Susumu Okuda, first edition, 1950, issued by CORONAPUBLISHING CO., LTD.). Hence, acid and basic materials have been usefulas curing agent.

However, the use along with curing agent has the following problems.That is, a composition combined with curing agent will be solidified,and hence it has poor long-term shelf life. This involves suchoperational complications that curing agent must be incorporated in acomposition for each coating operation.

Here, it is known that a composition in combination with curing agenthas the property of setting to gel for a short period of time andloosing fluidity; and that the speed at which the composition sets togel is affected by the type of curing agent and the amount of additionand temperature conditions of curing agent. Therefore, when coating acomposition combined with curing agent, the gelation of the compositionwill interfere with coating operation. Consequently, there arises suchcomplications in handling that, to retard the speed at which thecomposition sets to gel, it is necessary to make adjustment such as thedetermination of the type of curing agent or the modification of theamount of addition of curing agent.

SUMMARY OF THE INVENTION

In view of the problems in the above conventional technique, the presentinvention has as its object to provide a composition that may be usedfor such purposes as could not be handled satisfactorily in the past, byvirtue of the following characteristics: (1) It is possible to omit suchoperations as needed in the past that, in order to form a cured coatingfilm, the type of curing agent is selected, the amount of the curingagent is measured, and the curing agent is then added to and mixed witha composition, for each coating operation; (2) This composition can bepreserved stably for a long period of time by cutting off the atmosphere(water vapor and carbon dioxide); (3) This composition can form a curedcoating film by having it make a contact with the atmosphere, and can becured by heating at ordinary temperatures or low temperatures (40 to100° C.); (4) This composition can form a coating film excellent inwater resistance and non-flammability; (5) This composition can form acoating film having the function of generating the negative ion, thusbeing effective in deodorization, antibacterial activity, and organicmatter decomposition; and (6) The composition does not set to gelrapidly, permitting excellent operating performance.

The invention is a composition for coating obtained by incorporatingradioactive material (b) in alkali silicate (a) that can be expressed bythe general formula of M₂O.nSiO₂, (provided M is alkali metal, namelyNa, K, and Li; and n is a natural number), and imparting waterresistance to a film formed by the alkali silicate (a). The invention isalso a composition for coating that contains 1 to 25 parts by weight, interms of SiO₂, of the alkali silicate (a), 0.1 to 30 parts by weight ofthe radioactive material (b), and further 0 to 70 parts by weight ofinorganic filler (c), and 3 to 90 parts by weight of water (d), provided(a)+(b)+(c)+(d)=100 parts by weight. Specifically, the gist of theinvention resides in that the radioactive material (b) is mixed with thealkali silicate (a) and allowed to act thereon so as to form awaterproof bound film, containing 1 to 25 parts by weight, in terms ofSiO₂, of the alkali silicate (a), 0.1 to 30 parts by weight of theradioactive material (b), and 0 to 70 parts by weight of inorganicfiller (c), and 3 to 90 parts by weight of water (d), provided(a)+(b)+(c)+(d)=100 parts by weight.

The composition for coating of the invention produces the followingeffects. (1) This composition can form a waterproof film with alkalisilicate as binder, and the absence of flammable material enables anonflammable coating film to be formed. Therefore, this composition canbe applied to the surface of a flammable base material such as wood,paper, fabric, and the like, so that it can be used for the purpose ofimparting non-flammability to a base material;

(2) This composition can form a hard, nonflammable, and transparent orcolored coating film by applying and having it penetrate a porous basematerial such as concrete, slate plate and stone, alternatively, byapplying it to the surface of a metal base material such as zinc, ironand stainless steel. This protects the base material from fire andabrasion, or is suitable for coloring;

(3) It is known that since the formed film of organic binder is alreadychemically decomposed by the organic boding hand cutting action of thenegative ion, it deteriorates and then soon collapses if mixed with orused along with radioactive material. In contrast, with the compositionof the invention, the formed film of alkali silicate is inorganic anddoes not collapse by the negative ion. Hence, this composition is bestused for forming a coating film having the negative ion generatingfunction by applying it to a base material such as concrete, stone,wood, paper, fabric, and the like. That is, this composition can be usedfor coating purposes intended for non-flammable activity anddeodorization; and

(4) In coating, there is no need to mix curing agent, thus eliminatingannoyance with regard to the measuring and mixing of curing agent.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The components of a composition for coating according to the presentinvention will be described in detail.

Alkali silicate (a) used in the invention is silicate compound that canbe expressed by the general formula of M₂O.nSiO₂ (provided M is alkalimetal, namely Na, K, and Li; and n is a natural number), specifically,sodium silicate, potassium silicate, and lithium silicate, and that canform a thin film and act as binder, when dried at ordinary temperaturesor by heating. Provided the alkali silicate (a) is usually used in theform of aqueous solution. Therefore, the film that can be obtained bydrying only the component (a) at ordinary temperatures or by heating atlow temperatures is a film that can be obtained by dehydration, thuslacking water resistance. Consequently, a composition using thecomponent (a) as binder is unsuitable for coating purposes requiringwater resistance.

The present invention is based on the finding that a waterproof film canbe obtained by incorporating a component (b), namely radioactivematerial, in the alkali silicate (a). This eliminates the operation ofcombining a specific curing agent (described later) with the component(a). Specifically, when a composition with the alkali silicate (a) asbinder is used in combination with the component (b), although thecomponent (b) is material that belongs to neither acid nor basic, therearises such a phenomenon of imparting water resistance to the formedcoating film of the composition. Although it is difficult to specify thereason that the radioactive material imparts water resistance to theformed film of the component (a), it can be presumed that the followingactions have an effect on this. That is, there are known that, when theradioactive material (b) makes a direct contact with water vapor massand carbon dioxide concurrently in the atmosphere, radiation-chemicalreaction occurs; and that, in this reaction process (radiation-chemicalreaction process), hydrogen peroxide (H₂O₂) is generated on a contactsurface of the component (b), and the negative ion (H⁺) is released inthe atmosphere. Accordingly, the hydrogen peroxide and the negative iongenerated in the radiation-chemical reaction process, and carbon dioxide(double bond electron of carbon dioxide) act solely or jointly, so thatthe alkali silicate (a) can form waterproof silicate (see the article of“Polymerization of Silica” in the aforesaid book by Meyer).

The proportion of the component (a) of the invention is, in terms ofSiO₂, 0.1 to 30 parts by weight, preferably 0.5 to 20 parts by weight.Under 0.5 parts by weight, bonding strength may be poor. Over 20 partsby weight, it may take long for a coating film to have water resistance.

Component (b), namely radioactive material, used in the invention is inthe form of natural ore that generates radiation, or ceramic. As naturalore, there are materials containing an element that belongs to uraniumseries, actinium series, or thorium series. There are also ceramicsadjusted by using these materials.

The radioactive material (b) is necessary for allowing radiation to acton the alkali silicate (a), thereby imparting water resistance to asolidified film of the component (a).

It is desirable that the radioactive material (b) is in a fabric orparticle shape. Its average particle length or average particle diameteris not more than 100 μm, more preferably not more than 5 μm, withoutlimiting to this. The average particle length or average particlediameter of not more than 0.1 μm is advantageous for a compositionintended for purposes where it penetrates a base material. Over 10 μm,the coating film may have a rough surface.

It is desirable for safety in practice that the intensity of radiationof radioactive material (b) is not more than 370 becquerel/g, which isnot applicable to the regulation of the legislation regarding handling.More specifically, it is preferable to use radioactive material whoseradiation equivalent is 0.5 to 10 μSv (provided it is a value measuredby placing a Geiger counter at a position that is 5 mm away from theradioactive material). Below 0.5 μSv, it takes long for imparting waterresistance to a film formed by the component (a), which is unpractical.Over 10 μSv, the radiation is harmful to the human body, and it istherefore advisable not to use such material.

The proportion of the radioactive material (b) in a composition canchange depending on the dimension of the radiation equivalent of thecomponent (b). On the basis of radiation equivalent of 3 to 8 μSv(provided it is a measured value obtained by the above measuringmethod), it is 0.2 to 20 parts by weight, more preferably 0.5 to 10parts by weight. On the other hand, exceeding 10 parts by weight will beuneconomical because there is no significant difference in the speed ofimparting water resistance to the coating film of the composition.

To speedily allow the coating film to have water resistance, it ispreferable to increase the amount of addition of the component (b) inproportion to the amount of SiO₂ in a composition.

Component (c), namely inorganic filler, used in the invention ispreferably non-water-soluble and in the shape of particle or fabric. Itsaverage particle length or average particle diameter is 0.1 to 100 μm,more preferably not more than 0.5 to 30 μm. Below 0.5 μm, it is usefulfor purposes where a composition is allowed to permeate a base material.Over 30 μm, the coating film may have a rough surface.

As inorganic filler, there are inorganic body pigment, inorganicpigment, and metal powder. One or more than one type selected from thisgroup may be used as required.

Examples of inorganic body pigment are silica, talc, mullite, siliconcarbide, kaolin, and various whiskers. Examples of inorganic pigment areoxides of titanium, chrome, iron, manganese, and cobalt, as well as dualcomposite oxides consisting of one of these and aluminum. Examples ofmetal powder are tin, zinc, stainless steel, and nickel powders. Theseare cited merely by way of example and without limitation.

The proportion of the inorganic filler (c) in a composition ispreferably 0 to 70 parts by weight, more preferably 0 to 40 parts byweight. Over 40 parts by weight, the fluidity of the composition willdeteriorate, so that irregularities may occur in a coating film andoperating performance may be lowered.

The inorganic filler (c) is necessary for maintaining the thickness of acoating film formed by a composition, or performing coloring of acoating film. Hence, the component (c) can be omitted when a compositionis allowed to permeate a base material, or when no coloring is required.

Component (d), namely water, used in the invention is necessary foradjusting the viscosity of a composition, or the dispersion of theradioactive material (b) and the inorganic filler (c). Ion water,distilled water, and tap water can be used.

The proportion of water (d) in a composition is preferably 3 to 90 partsby weight, more preferably 30 to 70 parts by weight. Under 30 parts byweight, the ratio of alkali silicate (a), radioactive material (b), orinorganic filler (c) is increased thereby to lower the permeability orapplication performance with respect to a base material, and furthercause such a disadvantage that a coating film cannot turn into waterresistance speedily. Over 70 parts by weight of the component (d), thebonding strength is lowered to cause a coating film to be brittle insome cases. Note that the component (d) includes the water contained inthe component (a).

The present invention aims at imparting water resistance to a coatingfilm formed by a composition by having radioactive material (b) act onalkali silicate (a). Therefore, the composition of the invention doesnot become insoluble solidified matter unless it is exposed to theatmosphere so as to make a contact with water vapor mass and carbondioxide. This composition can exhibit excellent long-term shelf lifemerely by sealing it. There is also the characteristic that thecomposition can be used without the operations related to the selectionof curing agent, and the measuring and mixing of curing agent.

In a conventional manner, to impart water resistance to alkali silicate(a), acid or basic material is combined with the component (a) so as touse as curing agent. Specifically, acid material such as hydrochloricacid, aluminate, phosphoric acid, or basic material such as magnesiumoxide, zinc oxide, iron hydoroxide, barites, aluminum salt is used incombination with the component (a). However, when such curing agent iscombined and mixed with a composition with the component (a) as binder,the composition will set to gel, and hence the fluidity of thecomposition will be eliminated. This causes the disadvantages thatoperating performance is lowered, and that the composition incorporatingcuring agent cannot be preserved for a long period of time. Accordingly,the present invention aims at solving these problems.

The coating film formed by the composition of the invention iswaterproof, acid proof and nonflammable, and also has the negative iongenerating function, thereby having wide applications. For example, itcan be used in corrosion-resistant/weather-resistant decorative film formetal and concrete, nonflammable decorative film, thermal degradationpreventing film, and fire-resistant film for wood and paper. Inaddition, the negative ion generated from these films is available forthe fields of deodorization, fat splitting, and the like.

EXAMPLES

The present invention will be discussed more specifically with referenceto examples. However, it is to be understood that it is not limited tothe following examples, provided they do not exceed the scope of theinvention. In the examples, “unit (part)” and the symbol “%” are on thebasis of weight, unless otherwise noted.

The symbols used for representing components in the following tablesindicate as follows:

(a) Alkali Silicate

-   -   N: J-sodium silicate #3, (about 30% in SiO₂ concentration),        manufactured by Nippon Chemical Ind.    -   K: 1K potassium silicate (about 30% in SiO₂ concentration),        manufactured by Nippon Chemical Ind.    -   L: lithium silicate #45 (about 20% in SiO₂ concentration),        manufactured by Nippon Chemical Ind.

(b) Radioactive Material

-   -   M: monazite ore (natural radioactive material manufactured by        Serayamaichi, which is 1 μm in average particle diameter, and 5        to 7 μSv/5 mm of measuring distance in radiation dose        equivalent)    -   S: ceramic (composed of 38% moinazite, 28% anatase type titanium        dioxide, and 34% China clay, which is 1 μm in average particle        diameter, and 2 to 4 μSv/5 mm of measuring distance in radiation        dose equivalent)

(c) Inorganic Filler

-   -   C: chromium oxide (0.5 μm in average particle diameter, green        coloring agent)    -   T: talc (1 m in average particle diameter)    -   Z: zinc powder (2 μm in average particle diameter)

(d) Water

-   -   W: ion water

Experiment 1

Adjusted were 30 compositions shown in Tables 1, 2, and 3. In adjustingthe compositions, each of the components as shown in the tables was putin an agitator and agitated for 20 minutes at 200 r.p.m (revolutions perminute). This was then taken out and filtered with a 100-mesh sieve.TABLE 1 Mixing Component Type of Total Composition N M S C T Z W partsN-B1 10 90.0 100 N-1 10 0.5 89.5 100 N-2 10 0.5 89.5 100 N-3 10 5.0 85.0100 N-4 10 5.0 85.0 100 N-B2 30 5.0 5.0 5.0 55.0 100 N-5 30 5.0 5.0 5.05.0 55.0 100 N-6 30 5.0 5.0 5.0 5.0 50.0 100 N-B3 30 2.5 2.5 65.0 100N-7 30 2.5 2.5 5.0 5.0 5.0 50.0 100Provided N-B1 is blank.

TABLE 2 Mixing Component Type of Total Composition K M S C T Z W partsK-B1 10 90.0 100 K-1 10 0.5 89.5 100 K-2 10 0.5 89.5 100 K-3 10 5.0 85.0100 K-4 10 5.0 85.0 100 K-B2 30 5.0 5.0 5.0 55.0 100 K-5 30 5.0 5.0 5.05.0 55.0 100 K-6 30 5.0 5.0 5.0 5.0 50.0 100 K-B3 30 2.5 2.5 65.0 100K-7 30 2.5 2.5 5.0 5.0 5.0 50.0 100Provided K-B1 is blank.

TABLE 3 Mixing Component Type of Total Composition L M S C T Z W partsL-B1 10 90.0 100 L-1 10 0.5 89.5 100 L-2 10 0.5 89.5 100 L-3 10 5.0 85.0100 L-4 10 5.0 85.0 100 L-B2 30 5.0 5.0 5.0 55.0 100 L-5 30 5.0 5.0 5.05.0 55.0 100 L-6 30 5.0 5.0 5.0 5.0 50.0 100 L-B3 30 2.5 2.5 65.0 100L-7 30 2.5 2.5 5.0 5.0 5.0 50.0 100Provided L-B1 is blank.

Each of the 30 compositions shown in Tables 1 to 3 was applied by sprayto three iron plates (size: 70 mm×150 mm×1.2 mm), the weight of whichwas previously measured, and then allowed to stand indoors (roomtemperature 25° C., relative humidity 58%) for five days, so that thecomposition was dried to form a coating film. Thereafter, the weight wasmeasured again to calculate the weight (g) of the composition attachedto each of the iron plates. Each of the iron plates was then immersed indistilled water. After 24 hours, each plate was taken out of the water,and put in a drying oven to dry it. The weight of each plate wasmeasured to calculate the amount of decrease of the composition attachedto the plate, and the average amount of decrease (%) of the compositionsapplied to the three iron plates was calculated. The results are shownin Table 4. TABLE 4 Average Average Type of Average Type of loss Type ofloss Compo- loss Composition value (%) Composition value (%) sitionvalue (%) N-B1 36.28 K-B1 28.33 L-B1 16.07 N-1 11.25 K-1 10.48 L-1 7.79N-2 17.99 K-2 14.64 L2 9.52 N-3 8.41 K-3 5.77 L-3 3.22 N-4 9.67 K-4 8.12L-4 6.15 N-B2 45.82 K-B2 31.78 L-B2 25.93 N-5 5.03 K-5 4.41 L-5 3.33 N-68.46 K-6 6.17 L-6 4.09 N-B3 9.71 K-B3 8.29 L-B3 3.76 N-7 8.43 K-7 7.00L-7 3.30Provided B1 is blank.

Experiment 1 has disclosed that the radioactive material has the effectof imparting insolubility to the formed film of alkali silicate.

Experiment 2

The same composition as in Experiment 1 was applied to the dried slateplate (size: 300 mm×300 mm×5 mm) and dried by allowing it to standindoors for three days. A negative ion measuring apparatus (ITC-201A,manufactured by Alps Electric Co., Ltd.) was placed to measure theamount of the negative ion generated from the coating film. The resultsare shown in Table 5.

Provided the numerical value (piece/cc) of the negative ion amount shownin the table was obtained by correcting the measured value of thenegative ion amount generated from the coating film, based on thepreviously measured spontaneous negative ion amount existing indoors.TABLE 5 Measured values of the negative ion amount (MeasuringConditions: Room temp: 26° C.; Relative humidity: 54% Illumination:60-lux/fluorescent lamp) Measured Measured Measured Type of Value Typeof Value Type of Value Composition piece/cc Composition piece/ccComposition piece/cc N-B1 70 and below K-B1 70 and below L-B1 70 andbelow N-1 1870 K-1 1760 L-1 1930 N-2 1120 K-2 1200 L2 1270 N-3 6370 K-36670 L-3 6140 N-4 5280 K-4 5420 L-4 4970 N-B2 70 and below K-B2 70 andbelow L-B2 70 and below N-5 6520 K-5 6390 L-5 6450 N-6 5330 K-6 5930 L-65180 N-B3 4430 K-B3 4620 L-B3 4270 N-7 4390 K-7 4310 L-7 4110

Experiment 3

To examine the effect of deodorizing action on the negative iongenerated from each of the coating films formed by the compositions ofthe invention, 3-L ammonia gas adjusted to a predetermined concentrationwas admitted in two Tedlar-bags. A piece of drawing paper (size: 300mm×300 mm×5 mm), to both sides of which 35 g of the composition adjustedin Experiment 1 was applied previously, was put in one of the twoTedlar-bags. The other Tedlar-bag was empty (blank). The concentrationsof ammonia in the two Tedlar-bags were measured per elapsed time by adetector tube, and the measured values were compared. The types ofcompositions and the results of measurements are shown in Table 6. TABLE6 (Measuring Conditions: Room temp: 25° C.; Under irradiation of 500-luxfluorescent lamp) Concentration of ammonia (ppm) Type of InitialComposition concentration After 2 hours After 24 hours Blank 40. 34. 23.N-1 40. 13. Not more than 0.5 N-2 40. 20. Not more than 0.5 N-5 40. 2.Not more than 0.5 N-6 40. 3. Not more than 0.5 K-1 40. 12. Not more than0.5 K-2 40. 21. Not more than 0.5 K-5 40. 2. Not more than 0.5 K-6 40.4. Not more than 0.5 L-1 40. 15. Not more than 0.5 L-2 40. 20. Not morethan 0.5 L-5 40. 3. Not more than 0.5 L-6 40. 3. Not more than 0.5

Experiment 3 has disclosed that the coating films formed by thecompositions of the invention have deodorizing action.

Experiment 4

To examine how effectively the negative ion generated from the coatingfilm formed by the composition of the invention can perform the actionof decomposing organic matter, red ink (organic dye) was added dropwiseto each of the coating films of the compositions adjusted in Experiment2. The state in which the red ink was decomposed and faded away wasobserved with the naked eye, in order to determine the number of daysnecessary for the color of the ink to fade out. The results are shown inTable 7. This red ink was prepared by diluting a cartridge spare ink(product number IRF-12S-R), manufactured by PILOT Corporation, with 15times distilled water. With use of a syringe, 0.2 cc was added dropwiseonto each of the coating films of the compositions. TABLE 7 (MeasuringConditions: Under irradiation of indoor fluorescent lamp) Amount ofapplication of Number of days Type of Composition necessary for redcolor Composition (g/piece) to fade out Blank (slate plate) — Red colorremained after 240 days N-1 24. Within 60 days N-2 25. Within 60 daysN-3 24. Within 40 days N-4 26. Within 40 days N-5 24. Within 40 days N-625. Within 60 days

Experiment 4 has disclosed that the coating films formed by thecompositions of the invention generate the negative ion, and have theeffect of eliminating the coloring function of organic dye, thusexhibiting the action of decomposing organic matter.

Experiment 5

To examine the effect of the antibacterial action of the negative iongenerated from each of the coating films formed by the compositions ofthe invention, evaluation was made in the following manner. That is,Escherichia coli, Pseudomonas aeruginosa, yellow Staphylococcus, andMethicilin-Resistant Staphylococcus Aureus (MRSA) were respectivelyadded dropwise to individual stainless steel plates (size: 70 mm×70mm×1.8 mm), on which the compositions (N-5, K-5, and L-5) of theinvention was previously coated. After allowing these to stand for onehour, liquid bacteria was recovered by an applicator. Then, the numberof bacteria at the time of dropping and that at the time of recoverywere compared by microscopy, thus calculating the rate of decrease ofbacteria.

Method of Calculating Rate of Decrease of Bacteria:Rate of Decrease of Bacteria (%)={(Number of bacteria in recoveredliquid bacteria)÷(Number of bacteria in liquid bacteria at the time ofdropping)}×100

The results of the experiment was shown in Table 8, provided “blank”indicates the rate of decrease of bacteria in case of using a stainlesssteel plate without coating. TABLE 8 (Measuring Conditions: Room temp:25° C.; Under irradiation of 1000-lux fluorescent lamp) Type of bacteriaRate of decrease of bacteria after one hour (%) Type of EscherichiaPseudomonas Yellow Composition coil aeruginosa Saphylococcus MRSA Blank0. 0. 0. 0. N-5 99.9 99.9 99.9 99.9 K-5 99.9 99.9 99.9 99.9 L-5 99.999.9 99.9 99.9

Experiment 5 has disclosed that the coating films formed by thecompositions of the invention exhibit antibacterial property againstEscherichia coli, Pseudomonas aeruginosa, yellow Staphylococcus, andMRSA.

Experiment 6

Each of the compositions of the invention was applied to a stainlesssteel plate (size: 70 mm×150 mm×1.2 mm), and dried by allowing it tostand indoors for 24 hours. The obtained coating film was exposed to theflame of a gas burner (at temperatures of about 800° C.) for 60 seconds,in order to examine the presence or absence of fuming, the presence orabsence of the coating film peeling, and the change of appearance (thepresence or absence of burning trace). The results were shown in Table9. TABLE 9 Type of Coating Composition Fuming Film peeling Burning traceN-1 Nil Nil Nil N-2 Nil Nil Nil N-3 Nil Nil Nil N-4 Nil Nil Nil N-5 NilNil Nil N-6 Nil Nil Nil N-7 Nil Nil Nil K-1 Nil Nil Nil K-2 Nil Nil NilK-3 Nil Nil Nil K-4 Nil Nil Nil K-5 Nil Nil Nil K-6 Nil Nil Nil K-7 NilNil Nil L-1 Nil Nil Nil L-2 Nil Nil Nil L-3 Nil Nil Nil L-4 Nil Nil NilL-5 Nil Nil Nil L-6 Nil Nil Nil L-7 Nil Nil Nil

Experiment 6 has disclosed that the formed films of the compositions ofthe invention are nonflammable.

Experiment 7

Table 10 shows the results of measurements of the hardness of thecoating films formed by the compositions of the invention. Pencilshaving different hardness were used in the measurements. Scratching wasmade with the core of each pencil applied to the surface of the coatingfilm. There are shown the maximum values in the hardness of therespective pencils within the range of leaving no scar on the coatingfilm. TABLE 10 Coating Film Hardness Type of Composition Pencil hardnessN-5 7H N-6 7H K-5 7H K-6 7H L-5 5H L-6 5H

Experiment 7 has disclosed that the compositions of the invention canform a hard coating film.

The compositions of the invention may be coated on, for example, indoorconcrete, stone, and wood, so as to serve purposes such as odorelimination, nicotine decomposition, decomposition of volatile organicmatter that can cause sick house syndrome, and antibacterial activityagainst Escherichia coli, Pseudomonas aeruginosa, yellow Staphylococcus,and Methicilin-Resistant Staphylococcus Aureus (MRSA), as well as themaintenance of sanitation. Alternatively, the compositions may be coatedon metal so as to form a nonflammable decorative film, allowing it toperform the above actions. Hence, the compositions of the invention canbe used in such a wide range of applications as could not be handledsatisfactorily in the past.

1. A composition for coating obtained by incorporating radioactivematerial (b) in alkali silicate (a) that can be expressed by the generalformula of M₂O.nSiO₂ (provided M is alkali metal, namely Na, K, and Li;and n is a natural number), and imparting water resistance to a filmformed by the alkali silicate (a).
 2. The composition for coatingaccording to claim 1 that contains: 1 to 25 parts by weight, in terms ofSiO₂, of the alkali silicate (a); 0.1 to 30 parts by weight of theradioactive material (b); 0 to 70 parts by weight of inorganic filler(c); and 3 to 90 parts by weight of water (d), provided(a)+(b)+(c)+(d)=100 parts by weight.
 3. The composition for coatingaccording to claim 1 wherein, the radioactive material (b) isnon-water-soluble material having an average particle diameter oraverage length of not more than 100 μm, and is at least one selectedfrom the group consisting of ore having radioactivity and ceramic. 4.The composition for coating according to claim 1 wherein, the inorganicfiller (c) is non-water-soluble and has an average particle dimension oraverage length of 0.1 to 100 μm, and is at least one selected from thegroup consisting of inorganic body pigment, functional pigment, andmetal.
 5. A coating film having water resistance, acid resistance, andnon-flammability that can be formed by a composition for coatingaccording to one of claims 1 to 4.